Rheostat



(No Model.) 2 SheetsSheet 1,

A. B. HERRICK.

RHEOSTAT. No. 474,957. Patented May 17, 1892.

(No Model.) 2 Sheets-Sheet 2 A. B. HERRIGK.

RHEOSTATE No. 474,957. Patented May 17,1892.

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' UNITED STATES PATENT OEEIQE.

ALBERT l5. HERRICK, OF BAYONNE, NEW JERSEY.

RH EOSTAT.

SPECIFICATION forming part of Letters Patent No. 474,957, dated May 17,1892.

Application filed October 12, 1391. Serial No. 408,418. (No model.)

To all whom it may cmwcrn:

Be it known that I, ALBERT B. IIERRICK,L citizen of the United States,residing at Bayonne, in the county of Hudson and State of New Jersey,have invented a certain new and usefulImprovement in Rheostats orRegulators, of which the following is a specification.

The present invention relates to devices for regulating the resistancein electrical circuits, and especially for regulating dynamos and forcutting in or cutting out the resistance gradually by forming a largenumber of subdivisions of the resistance-conductor. The rheostat to bedescribed belongs to that class in which a resistance-conductor isinsulated for most of its length, but is bare along the path of a switcharm or device, so that said arm or device rubs (lirectlyon the conductorand no special contact-blocks are needed for said arm to travel over.

The objects of the invention are primarily to obtain an economical,simple, and efiicient construction for such rheostats.

In the accompanying drawings, Figure 1 is a plan view of one form of theresistance. Fig. 2 is a cross-section of Fig. 1 on line 00 00. Fig. 3 isa side view of a modified form, the side of the inclosing case beingremoved. Fig. 4 is a view at right angles to Fig. 3, and Figs. 5 and 6are detail views for showing the circuit connections.

In the switch to be first described 1 is a cast-iron or other suitablefire-proof inclosing box or frame for the resistance devices. Theresistance-00nductor is preferably in two sections, each section beingwound on a frame, which is substantiallyrectangular and which consistsof two insulating and heat-resisting or fire-proof plates 2, preferablyof slate, which are held paralleland at a suitable distance apart byposts 3. These posts, instead of being made continuous, as shown at theright of Fig. 2, may be made shorter and tubular, as indicated at theleft of Fig. 2, and may be extended by means of the rods at, spiralsprings 5 being placed, as shown, to press the plates apart. Theresistanceconduetors 6 are mounted 011 these frames. Before being woundthe conductor is insulated throughout its length. The frames, with theirconductors, are mounted on each side of the spindle 7 of a switch-arm 8,and the insulating material is removed from the surface of theconductors in arcs corresponding to those over which the two ends of theswitch-arm move. These uninsulated portions of the conductor areindicated by the light spaces 9. One wire of the circuit in which theresistance is to be inten posed is connected to the block 10, to whichan end of one of the resistance-conduetors is connected, and the otherwire is connected to the block 11, to which the opposite end of theother resistance-conductor is connected.

12 13 are idle contacts, on which the switcharm rests when the circuitis open. The first movement of the switch-arm will throw the said armonto the bared resistance-conductor at the two opposite ends, throwingthe whole of both of said conductors into the circuit. As the arm ismoved forward the successive turns of the two conductors are thrown outof circuit, thereby very gradually reducing the effective resistance anddoing it without sparking, owing to the small difference of potentialbetween adjoining turns of the cond uctors until when the switch reachesthe limit of its movement a complete short eircuit through the rheostatis closed.

In the switch illustrated in Figs. 3 and t the frames on which theconductors are wound are of different construction, being composed ofside plates 14; 15, held in proper relative position by cross-blocks 16and having their upper edge in the form of an arc of a circle the centerof which is at the pivot 18, which carries the switch-arm 19 and handle20. A resistanceconductor G is wound on each of the two frames,constructed as described, and said conductors are bared along the uppercurved surfaces or edges on which the switch-contacts 21, carried by thespring-arm 22, are moved. The two frames, with their conductors, aremounted in cast-iron or other suitable frames 23, which are securedtogether by rods 24: and which are provided with ledges 25, around whicha wire screen 26 is secured. At one end of the contact-edge of theframes described are idle-contacts 27, on which the switch-contacts 21rest when the switch is in its open position. Beside these contacts arecontacts 28, to which ends of the resistancecondn'ctors are connected.At the opposite ends of the frames are contacts 29, to which theopposite ends of the resistance conductors are connected. The circuit ofthis resistance device is indicated in Fig. 5, one wire entering at 29011 one side of the switcharm and the other wire connecting with theopposite contact 20. WVhile the switch-arm rests on the contacts 27 thecircuit is open; but when it is moved forward the entire resistance isthrown into the circuit and is then gradually cut out, as alreadydescribed. I may connect the resistance-conductors end to end, asindicated at 3o, Fig.6. In this case the operation of the rheostat wouldbe slightly different, since the switch-arm would serve merely toshort-circuit more or less of the resistance in an obvious manner, andthis I find very useful when the rheostat is used-for example, forregulating dynamics-since the field-circuit would not be accidentallyopened by a failure of the switch-arm to make connection with theresistance-00nductor, owing to accumulation of dirt or other cause, aswould be the case with the circuit connections first described.Evidently this cross connection may be applied to either form ofrheostat. It will be seen that the connection described can be made ofvery cheap material, and very little skill is required in putting thedevice together, and the wholedevice is practically fire-proof. Thewires or resistance-conductors, being wound on the open frames, have thelargest possible amount of surface exposed to the cooling influence ofthe air and any expansion or contraction which occurs, owing to changesin temperature of the conductors, will be compensated for by operationof the springs 5 if such springs are employed. Ordinarily, however,there will be so little expansion and contraction, owing to theshortness of each turn of wire, that it will not be necessary to guardagainst them.

In Fig. 2 a wedge '10 is shown between the plate 1 at the bottom and theconductor wound on the frame. Said wedge serves to tighten the conductorand also to still further admit air around it.

hat I claim is 1. The combination, in a rheostat, of two stationaryinsulating-frames or open structures, a resistance-conductor wound oneach frame, and aswitch device the opposite ends of which are movableover the resistance-conductors, said conductors being uninsulated in thepath of movement of the switch device, substantially as described.

2. The combination, in a rheostat,of a stationary body, aresistance-00nductor wound thereon, and a switch device movable in anare over the resistance-00nd nctor, said conductor being uninsulated inthe path of movement of the switch-arm, whereby contact is made directlywith the successive turns of the conductor, substantially as described.

3. The combination, in a rheostat, of a stationary body consisting of aninsulating-frame or open structure, a resistance conductorwound thereon,whereby the outer surface and a large part of the inner surface of theconductor will be open to the air, and a switch device movable overtheresistance-conductor, said conductor being uninsulated in the path ofmovement of the switch-arm, whereby contact is made directly with thesuccessive turns of the conductor,substantially as described.

4. The combination, in a rheostat, of a stationary body consisting of aninsulating fireproof open structure, a resistance-00nductor woundthereon, and a switch device movable over the resistance-00nductor, saidconductor being uninsulatcd in the path of movement of the switch-arm,whereby contact is made directly with the successive turns of theconductor, substantially as described.

5. The combination, in a rheostat, of a stationary fire-proof body, aninsulated resistance-conductor thereon, and a switch device movable overthe resistance-00ndnctor, said conductor being uninsulatcd in the pathof movement of the switch-arm, the supporting body being constructed asan open frame or structure to allow air to circulate around theconductor through a large part of its length, substantially asdescribed.

(3. The combination, in a rheostat, of a resistance in two connectedsections and connected or adapted to be connected to a circuit, and amovable-switch device the opposite ends of which make contact with thetwo sections of resistance-00nductor, whereby as the switch is movedresistance is cut in or out, but the circuit is not opened by accidentalfailure of contactbetween the switch-arm and conductor, substantially asdescribed.

This specification signed and witnessed this 1st day of October, 1891.

ALBERT B. IIERRICK.

Witnesses:

J OHN MCGLUE, E. A. STEVENSON.

